What console command do you use? I don't think it's quest related, you can find dwarven bolts in dwemer ruins before any quest for example . The wiki codes begin with XX but you should replace XX by 02 (I don't know why they don't give exact codes). You can see exact codes ingame when you have the items. So an enhanced dwarven crossbow is 0200f19f and dwarven bolts 0200d099. Other codes here : http://elderscrolls.wikia.com/wiki/Bolts_%28Dawnguard%29
The xx stands for your load order. Some people may not have Dawnguard up second. It's a good idea to move Dawnguard up to number 2 if you have mods etc, in any case.
Also make sure you put the number you want after the code or you will get an error. ie:
player.additem 0200F19E 1 (1 crossbow)
player.additem 0200D099 100 (100 bolts)